Vocal cord paralysis and paresis are debilitating conditions leading to difficulty with voice production. The alterations in voice production are usually severe enough to impede the individual's ability to work and to conduct normal social interactions. Medialization laryngoplasty is a surgical procedure designed to restore voice in patients with glottal insufficiency due to incomplete vocal fold adduction. The objective of the procedure is to implant a uniquely configured (i.e. patient specific) structural support lateral to the paretic vocal fold in order to bring it into close proximity with the normal vocal fold of the opposite side. The implant is placed through a window cut in the thyroid cartilage. However, the revision rate for the procedure is as high as 24%. In an effort to improve the success rate, the work of this proposal will contribute to the development of a pre-operative planning system that will determine the optimal location and configuration of the implant and an intra-operative image-guided system that will ensure exact placement. Three dimensional computer-modeling based on preoperative CT datasets will create a patient-specific model of the laryngeal cartilage and vocal folds, with and without implant. Computational fluid dynamics will simulate vocal fold vibration associated with voice production and will define the best possible position and configuration for the implant. Intra-operative image guidance will be performed by registering a pre-operative 3D CT image with 2D visual images of the operating field generated during the operation. The system will allow the surgeon to "see through" the operating field of the thyroid cartilage and visualize the precise location of the underlying vocal fold. The short-term goal is to improve the clinical outcomes of medialization laryngoplasty, which in turn will reduce revision rates and health care costs associated with them. The long-term significance is to solve fundamental problems associated with the biomechanical modeling and simulation of voice production and problems associated with the use of intra-operative 2D imagery in image-guided surgical procedures.